The hormone hCG, or human chorionic gonadotropin, is a hormone produced by a portion of a developing embryo that helps to maintain pregnancy. The pharmaceutical called Pregnyl is a purified form of hCG that physicians use to help stimulate ovulation in women who have certain types of infertility.
Significance
Adult humans, regardless of gender and whether they're pregnant, don't produce hCG, explains Dr. Lauralee Sherwood in her book "Human Physiology." Rather, hCG comes from tissue in a developing embryo beginning soon after fertilization. As the embryo develops, the hCG-secreting portion of the embryo begins to differentiate, or become a specific tissue type. This tissue is called the chorion, of which the placenta is a portion. As such, the hCG hormone occurs only in the blood of a pregnant woman.
Function
The purpose of hCG in a pregnant woman's body is to help maintain the lining of the uterus. Each month before you ovulate, your uterine lining thickens, explains Dr. Gary Thibodeau in his book "Anatomy and Physiology." About 14 days after ovulation, the lining is shed. In the event that an ovulated egg meets sperm and is fertilized, it will need to implant in the uterine lining. As such, the fertilized egg secretes hCG, which signals your body to maintain the lining of the uterus.
Effects
Because of its structural similarity to another hormone, LH, or luteinizing hormone, it's possible to use concentrated hCG as a pharmaceutical. LH is a hormone produced by a portion of your brain called the anterior pituitary gland, explains Dr. Thibodeau. The purpose of the hormone in women is to stimulate ovulation. Some women experience infertility because they have low LH secretion and, therefore, don't ovulate. In these individuals, physicians may be able to stimulate ovulation with hCG injections.
Considerations
Pharmaceutically available hCG is sold under the brand name Pregnyl. It's obtained from the urine of pregnant women, explains RxList.com, and is biologically purified so that it doesn't contain any of the original components of the urine other than the hCG hormone. The shape of hCG is quite similar to the shape of LH, such that if a physician injects hCG into a woman who is not pregnant, her body will respond to the hCG as if it were LH.
Expert Insight
Pregnyl isn't used to treat all forms of infertility in women; there are many types of infertility and they have a variety of causes and treatments. Only women who fail to conceive because they don't ovulate stand to benefit from Pregnyl; those who have other underlying causes of infertility will not benefit from injections. RxList.com notes that side effects include increased potential for development of a blood clot because Pregnyl changes the pattern of blood flow and speed of blood flow, particularly in the deep veins of the legs.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
- RXList: Pregnyl
